What kind of wire to hook up my EV?

I have an EV12L that I want to bring back into commission. I bought 14-gauge wire to hook it back but the wire is too thick to get into the holes via the "push pins" (heck - it's even a challenge to solder the wire into the 1/4 inch right-angle jack!). Can I use 16-guage or should I just try to force the wires in and trim the excess copper threads?

The speaker is 300 watts and I was told that I should stick with the 14-gauge.